Methods are described for the selection of bacterial mutants possessing altered or missing specific surface antigens. These methods will be used to isolate teichoic acid mutants of Streptococcus mutans and Actinomyces Viscosus, in order to study the role of this surface component in mediating the attachment of oral pathogens to tooth surfaces. In addition, a general selection is described for the isolation of mutants of Strep mutans defective in the attachment process. Isolation of such mutants will permit the direct identification of the component(s) essential for the glucan-dependent and -independent affinity of this bacteria for enamel. In vivo studies will be used to confirm the role of particular surface components in the attachment process under naturally occurring conditions.